I once used the autotag feature of the web-admin and had something similar happen. It went tag happy and would apply tags for all media of similar names regardless of type. My attributes for a single cd audio track had 10-15 attributes for movies. I didn't look at the id3 files after doing this but imagine they would have been pretty loaded.

i suddenly realized that in mainly all media directories, where an id3 file exists, a lot of other files with the same name exists, but with a appendix.

e.g.

ld.id3ld.id3.0oZE5qld.id3.1o9VVhld.id3.2eYcuf...

This happens continuously on my NAS as well, with LinuxMCE, not Dianemo. I never chased it down completely. It looked to me like something with UpdateMedia and tmp files while writing id3s. Hundreds of these files build up on my NAS.